Submerged gas evaporators and reactors

ABSTRACT

A submerged gas processor in the form of an evaporator or a submerged gas reactor includes a vessel, a gas delivery tube partially disposed within the vessel to deliver a gas into the vessel and a process fluid inlet that provides a process fluid to the vessel at a rate sufficient to maintain a controlled constant level of fluid within the vessel. A weir is disposed within the vessel adjacent the gas delivery tube to form a first fluid circulation path between a first weir end and a wall of the vessel and a second fluid circulation path between a second weir end and an upper end of the vessel. During operation, gas introduced through the tube mixes with the process fluid and the combined gas and fluid flow at a high rate with a high degree of turbulence along the first and second circulation paths defined around the weir, thereby promoting vigorous mixing and intimate contact between the gas and the process fluid. This turbulent flow develops a significant amount of interfacial surface area between the gas and the process fluid resulting in a reduction of the required residence time of the gas within the process fluid to achieve thermal equilibrium and/or to drive chemical reactions to completion, all of which leads to a more efficient and complete evaporation, chemical reaction, or combined evaporation and chemical reaction process.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to devices that mix gases andliquids, and more specifically, to submerged gas processors includingsubmerged gas evaporators and submerged gas reactors.

BACKGROUND

Submerged gas evaporators, submerged gas reactors and combinationsubmerged gas evaporator/reactor systems in which gas is dispersedwithin the liquid phase, referred to generally herein as submerged gasprocessors, are well known types of devices used in many industries toperform evaporation and chemical reaction processes with respect tovarious constituents. U.S. Pat. No. 5,342,482, discloses a common typeof submerged combustion gas evaporator, in which combustion gas isgenerated and delivered though an inlet pipe to a dispersal unitsubmerged within the liquid to be evaporated. The dispersal unitincludes a number of spaced-apart gas delivery pipes extending radiallyoutward from the inlet pipe, each of the gas delivery pipes having smallholes spaced apart at various locations on the surface of the gasdelivery pipe to disperse the combustion gas as small bubbles asuniformly as practical across the cross-sectional area of the liquidheld within the processing vessel. According to current understandingwithin the prior art, this design provides desirable intimate contactbetween the liquid and the combustion gas over a large interfacialsurface area while also promoting thorough agitation of the liquidwithin the processing vessel.

Because submerged gas processors do not employ heat exchangers withsolid heated surfaces, these devices provide a significant advantagewhen compared to conventional evaporators or chemical reactors whencontact between a liquid stream and a gas stream is desirable. In fact,submerged gas processors are especially advantageous when the desiredresult is to highly concentrate a liquid stream by means of evaporation.

However, many feed streams, prior to reaching a desired concentration,produce solids in the form of precipitates that are difficult to handle.These precipitates may include substances that form deposits on thesolid surfaces of heat exchangers used in conventional evaporators, andsubstances that tend to form large crystals or agglomerates that canblock passages within processing equipment, such as the gas exit holesin the system described in U.S. Pat. No. 5,342,482. Generally speaking,feed streams that cause deposits to form on surfaces and createblockages within process equipment are called fouling fluids.

Additionally, common problems within conventional evaporation andchemical reaction systems used for processing fouling fluids includedeterioration of the rate of heat transfer over time due to the buildupof deposits on solid heat exchange surfaces and equipment malfunctionsrelated to blockages in critical locations such as gas outlet pipes.These common problems adversely affect the efficiency and costs ofconventional processes in that the potential for buildup of deposits andblockages necessitate frequent cleaning cycles to avoid sudden failureswithin the evaporation or reaction equipment.

Additionally, most evaporation and chemical reactor systems that rely onintimate contact between gases and liquids are prone to problems relatedto carryover of entrained liquid droplets that form as the vapor phasedisengages from the liquid phase. For this reason, most evaporator andchemical reactor systems that require intimate contact of gas withliquid include one or more devices to minimize entrainment of liquiddroplets and/or to capture entrained liquid droplets while allowing forseparation of the entrained liquid droplets from the exhaust gas flowingout of the evaporation zone. The need to mitigate carryover of entrainedliquid droplets may be related to one or more factors includingconformance with environmental regulations, conformance with health andsafety regulations and controlling losses of material that might havesignificant value.

Unlike conventional evaporators and reactors where heat is transferredto the material being processed through heat exchangers with solidsurfaces, heat and mass transfer within submerged gas processors takeplace at the interface of a discontinuous gas phase dispersed within acontinuous liquid phase. Compared to the fixed solid heat transfersurfaces employed in conventional evaporators and reactors, foulingfluids cannot coat the heat transfer surface within submerged gasprocessors as new surface area is constantly being formed by a steadyflow of gas which is dispersed within the liquid phase and remains incontact with the liquid for a finite period of time before disengaging.This finite period of time is called the residence time of the gaswithin the evaporation, or evaporation/reaction zone.

Submerged gas processors also tend to mitigate the formation of largecrystals because dispersing the gas beneath the liquid surface promotesvigorous agitation within the evaporation or the evaporation/reactionzone, which is a less desirable environment for crystal growth than amore quiescent zone. Further, active mixing within an evaporation orreaction vessel tends to maintain precipitated solids in suspension andthereby mitigates blockages that are related to settling and/oragglomeration of suspended solids.

However, mitigation of crystal growth and settlement is dependent on thedegree of mixing achieved within a particular submerged gas processor,and not all submerged gas processor designs provide adequate mixing toprevent large crystal growth and related blockages. Therefore, while thedynamic renewable heat transfer surface area feature of submerged gasprocessors eliminates the potential for fouling liquids to coat heatexchange surfaces, conventional submerged gas processors are stillsubject to potential blockages and carryover of entrained liquid withinthe exhaust gas flowing away from the evaporation zone.

Direct contact between hot gas and liquid undergoing processing within asubmerged gas processor provides excellent heat transfer efficiency. Ifthe residence time of the gas within the liquid is adequate for the gasand liquid temperatures to equalize, a submerged gas processor operatesat a high level of overall energy efficiency. For example, when hot gasis dispersed in a liquid that is at a lower temperature than the gas andthe residence time is adequate to allow the gas and liquid temperaturesto attain the adiabatic operating temperature for the system, all of theavailable driving force of temperature differential will be used totransfer thermal energy from the gas to the liquid. The minimumresidence time to attain equilibrium of gas and liquid temperatureswithin the evaporation, reaction or combined reaction/evaporation zoneof a submerged gas processor is a function of factors that include, butare not limited to, the temperature differential between the hot gas andliquid, the properties of the gas and liquid phase components, theproperties of the resultant gas-liquid mixture, the net heat absorbed orreleased through any chemical reactions and the extent of interfacialsurface area generated as the hot gas is dispersed into the liquid.

Given a fixed set of values for temperature differential, properties ofthe gas and the liquid components, properties of the gas-liquid mixture,heats of reaction and the extent of the interfacial surface area, theresidence time of the gas is a function of factors that include thedifference in specific gravity between the gas and liquid or buoyancyfactor, and other forces that affect the vertical rate of rise of thegas through the liquid phase including the viscosity and surface tensionof the liquid. Additionally, the flow pattern of the liquid includingany mixing action imparted to the liquid such as that created by themeans chosen to disperse the gas within the liquid affect the rate ofgas disengagement from the liquid.

Submerged gas processors may be built in various configurations. Onecommon type of submerged gas processor is the submerged combustion gasevaporator that generally employs a pressurized burner mounted to a gasinlet tube that serves as both a combustion chamber and as a conduit todirect the combustion gas to a dispersion system located beneath thesurface of liquid held within an evaporation vessel. The pressurizedburner may be fired by any combination of conventional liquid or gaseousfuels such as natural gas, oil or propane, any combination ofnon-conventional gaseous or liquid fuels such as biogas or residual oil,or any combination of conventional and non-conventional fuels.

Other types of submerged gas processors include hot gas evaporatorswhere hot gas is either injected under pressure or drawn by an inducedpressure drop through a dispersion system located beneath the surface ofliquid held within an evaporation vessel. While hot gas evaporators mayutilize combustion gas such as hot gas from the exhaust stacks ofcombustion processes, gases other than combustion gases or mixtures ofcombustion gases and other gases may be employed as desired to suit theneeds of a particular evaporation process. Thus, waste heat in the formof hot gas produced in reciprocating engines, turbines, boilers or flarestacks may be used within hot gas evaporators. In other forms, hot gasevaporators may be configured to utilize specific gases or mixtures ofgases that are desirable for a particular process such as air, carbondioxide or nitrogen that are heated within heat exchangers prior tobeing injected into or drawn through the liquid contained within anevaporation vessel.

Regardless of the type of submerged gas processor or the source of thegas used within a processor, in order for the process to continuouslyperform effectively, reliably and efficiently, the design of thesubmerged gas processor must include provisions for efficient heat andmass transfer between gas and liquid phases, control of entrained liquiddroplets within the exhaust gas, mitigating the formation of largecrystals or agglomerates of particles and maintaining the mixture ofsolids and liquids within the submerged gas processing vessel in ahomogeneous state to prevent settling of suspended particles carriedwithin the liquid feed and/or precipitated solids.

SUMMARY OF THE DISCLOSURE

A simple and efficient submerged gas processor includes an evaporation,reaction or combination evaporation/reaction vessel, a tube partiallydisposed within the vessel which is adapted to transport a gas into theinterior of the vessel, a process fluid inlet adapted to transport aprocess fluid into the vessel at a rate that maintains the process fluidinside the vessel at a predetermined level and an exhaust stack thatallows spent gas to flow away from the vessel. In addition, thesubmerged gas processor includes a weir disposed within the reactionvessel. The weir may at least partially surround the tube and may besubmerged in the process fluid to create a fluid circulation path aroundthe weir within the vessel. In one embodiment, the weir is open at bothends and forms a lower circulation gap between a first one of the weirends and a bottom wall of the vessel and an upper circulation gapbetween a second one of the weir ends and a normal process fluidoperating level.

During operation, gas introduced through the tube mixes with the processfluid in a first confined volume formed by the weir, and the fluidmixture of gas and liquid flows at high volume with a high degree ofturbulence along the circulation path defined around the weir, therebycausing a high degree of mixing between the gas and the process fluidand any suspended particles within the process fluid. Shear forceswithin this two-phase or three-phase turbulent flow that result from thehigh density liquid phase overrunning the low density gas phase createextensive interfacial surface area between the gas and the process fluidthat favors minimum residence time for mass and heat transfer betweenthe liquid and gas phases to come to equilibrium compared toconventional gas dispersion techniques. Still further, vigorous mixingcreated by the turbulent flow hinders the formation of large crystals ofprecipitates within the process fluid and, because the system does notuse small holes or other ports to introduce the gas into the processfluid, clogging and fouling associated with other submerged gasprocessors are significantly reduced or entirely eliminated. Stillfurther, the predominantly horizontal flow direction of the liquid andgas mixture over the top of the weir and along the surface of theprocess fluid within the processing vessel enables the gas phase todisengage from the process fluid with minimal entrainment of liquid dueto the significantly greater momentum of the much higher density liquidthat is directed primarily horizontally compared to the low density gaswith a relatively weak but constant vertical momentum component due tobuoyancy.

In addition, a method of processing fluid using a submerged gasprocessor includes providing a process fluid to a vessel of a submergedgas processor at a rate sufficient to maintain the fluid level at apredetermined level within the vessel, supplying a gas to the vessel,and mixing the gas and process fluid within the vessel by causing thegas and process fluid to flow around a weir within the submerged gasprocessor to thereby transfer heat energy and mass between the gas andliquid phases of a mixture and/or to otherwise react constituents withinthe gas and liquid phases of a mixture.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a submerged gas processorconstructed in accordance with the teachings of the disclosure.

FIG. 2 is a cross-sectional view of a second submerged gas processorincluding a baffle.

FIG. 3 is a cross-sectional view of a third submerged gas processorhaving a tubular shaped weir.

FIG. 4 is a top plan view of the submerged gas processor of FIG. 3.

FIG. 5 is a cross-sectional view of a fourth submerged gas processorconnected to a source of waste heat.

FIG. 6 is a cross-sectional view of a submerged gas processor having aheating blanket disposed around an exterior portion thereof.

DETAILED DESCRIPTION

Referring to FIG. 1, a submerged gas processor 10, in the form of asubmerged combustion gas evaporator, includes a burner 20 and a hot gassupply tube or gas inlet tube 22 having sparge or gas exit ports 24 ator near an end 26 thereof. The gas inlet tube 22 is disposed within anevaporator vessel 30 having a bottom wall 31 and a process fluid outletport 32. A process fluid inlet port 34 is disposed in one side of thevessel 30 and enables a process fluid 35 (and other liquids) to beprovided into the interior of the vessel 30. Additionally, a weir 40,which is illustrated in FIG. 1 as a flat or solid plate member having afirst or lower end 41 and a second or upper end 42, is disposed withinthe vessel 30 adjacent the gas inlet tube 22. The weir 40 defines andseparates two volumes 70 and 71 within the vessel 30. As illustrated inFIG. 1, a gas exit port 60 disposed in the top of the vessel 30 enablesgas to exit from the interior of the vessel 30.

In the submerged combustion gas evaporator of FIG. 1, the burner 20,which may be a nozzle mix or pre-mix type of pressurized burner, issupplied with fuel under pressure from a blower or pump (not shown inFIG. 1) through a line 51 and is supplied with air under pressure from ablower (not shown in FIG. 1) through a line 53. Moreover, the processfluid 35 may be supplied through the fluid inlet 34 by a pump (not shownin FIG. 1) at a rate sufficient to maintain a surface 80 of the processfluid 35 within the vessel 30 at a predetermined level, which may be setby a user. A level sensor and control (not shown in FIG. 1) may be usedto determine and control the rate that the process fluid 35 is suppliedthrough the inlet port 34.

As illustrated in FIG. 1, the weir 40 is mounted within the vessel 30 toform a lower circulation gap 36 between the first end 41 of the weir 40and the bottom wall 31 of the vessel 30 and to form an upper circulationgap 37 between the second end 42 of the weir 40 and the surface 80 ofthe process fluid 35 (or the top wall of the vessel 30). As will beunderstood, the upper end 42 of the weir 40 is preferably set to be ator below the surface level 80 of the process fluid 35 when the processfluid 35 is at rest (i.e., when no gas is being introduced into thevessel via the gas inlet tube 22). In some situations, it may bepossible to set the upper end 42 of the weir 40 slightly above the atrest level of the process fluid 80, as long as introduction of the gasvia the gas inlet tube 22 still causes liquid to flow over the upper end42 of the weir 40. In any event, as illustrated in FIG. 1, the weir 40also defines and separates the confined volume or space 70 in which thesparge ports 24 are located from the volume or space 71. If desired, theweir 40 may be mounted to the vessel 30 via welding, bolts or otherfasteners attached to internal side walls of the vessel 30.

During operation, a pressurized mixture of gas and air from the lines 51and 53 is ignited within the burner 20 and is forced to flow underpressure into and through the gas inlet tube 22 where combustion of thefuel is completed before the combusted fuel/air mixture (hereinafter“combustion gas”) reaches the sparge or exit ports 24. The combustiongas exits the gas inlet tube 22 through the sparge ports 24 into theconfined volume 70 formed between the weir 40 and the gas inlet tube 22,causing the combustion gas to be dispersed into the continuous liquidphase of the process fluid within the vessel 30. Generally speaking, gasexiting from the sparge ports 24 mixes with the liquid phase of theprocess fluid within the confined volume 70 and causes a high volumeflow pattern to develop around the weir 40. The velocity of the flowpattern and hence the turbulence associated with the flow pattern ishighest within the confined volume 70 and at the locations where theliquid flows through the upper gap 37 and the lower gap 36 of the weir40. The turbulence within the confined volume 70 significantly enhancesthe dispersion of the gas into the process fluid which, in turn,provides for efficient heat and mass transfer between the gas and theprocess fluid. In particular, after exiting the sparge ports 24, thecombustion gas is dispersed as a discontinuous phase into a continuousliquid phase of the process fluid forming a gas/liquid mixture withinthe confined volume 70. The mass per unit volume of the gas/liquidmixture in the confined volume 70 is significantly less than that of thecontinuous liquid phase of the process fluid in the volume 71. Due tothis large difference in mass per unit volume of the liquid compared tothe gas, typically on the order of approximately 1000 to 1, a differencein static hydraulic pressure is formed between the gas/liquid mixture inthe confined volume 70 and the liquid phase in the volume 71 at allelevations. This imbalance in static hydraulic pressure forces theprocess fluid to flow from the higher pressure region, i.e., the volume71, to the lower pressure region, i.e., the confined volume 70, at arate that overcomes the impressed static hydraulic pressure imbalanceand creates flow upward through the confined volume 70.

Put another way, the dispersion of gas into the process fluid 35 withinthe confined volume 70 at the sparge ports 24 develops a continuous flowpattern that draws process fluid 35 under the bottom edge 41 of the weir40 through the lower circulation gap 36, and causes the mixture of gasand process fluid 35 to move through the confined volume 70 and towardthe surface 80 of the process fluid 35. Near the surface 80, thegas/liquid mixture reaches a point of balance at which the imbalance ofstatic hydraulic pressure is eliminated. Generally speaking, this pointis at or near the upper circulation gap 37 formed between the second end42 of the weir 40 and the process fluid surface 80. At the balancepoint, the force of gravity, which becomes the primary outside forceacting on the gas/fluid mixture, gradually reduces the vertical momentumof the gas/liquid mixture to near zero. This reduced vertical momentum,in turn, causes the gas/liquid mixture to flow in a predominantlyhorizontal direction over the second end 42 of the weir 40 (through thecirculation gap 37 defined at or near the surface 80 of the processfluid 35) and into the liquid phase of the process fluid 35 within thevolume 71.

This flow pattern around the weir 40 affects the dispersion of thecombustion gas into the continuous liquid phase of the process fluid 35and, in particular, thoroughly agitates the continuous liquid phase ofthe process fluid 35 within the vessel 30 while creating a substantiallyhorizontal flow pattern of the gas/liquid mixture at or near the surface80 of the continuous liquid phase of the process fluid 35. Thishorizontal flow pattern significantly mitigates the potential forentrained liquid droplets to be carried vertically upward along with thedispersed gas phase as the dispersed gas phase rises through the liquidphase due to buoyancy and finally disengages from the continuous liquidphase of the process fluid at the surface 80 of the process fluid 35.

Also, the mixing action created by the induced flow of liquid andliquid/gas mixtures within both the confined volume 70 and the volume 71hinders the formation of large crystals of precipitates, which generallyrequires a quiescent environment. By selectively favoring the productionof relatively small particles of precipitates, the mixing action withinvessel 30 helps to ensure that suspended particles formed in thesubmerged gas evaporation process may be maintained in suspension withinthe liquid phase circulating around the weir 40, which effectivelymitigates the formation of blockages and fouling within the submergedgas evaporator. Likewise, because relatively small particles that arereadily maintained in suspension are formed through precipitation, theefficiency of the evaporator is improved over conventional evaporationsystems in terms of freedom from clogging and fouling and the degree towhich the feed liquid may be concentrated.

In addition, as the circulating liquid phase within volume 71 approachesthe bottom wall 31 of the vessel 30, the liquid phase is forced to flowin a predominantly horizontal direction and through the lower gap 36into the confined volume 70. This predominantly horizontal flow patternnear the bottom wall 31 of the vessel 30 creates a scouring action atand above the interior surface of the bottom wall 31 which maintainsparticles of solids including precipitates in suspension within thecirculating liquid while the submerged combustion gas evaporator isoperating. The scouring action at and near the bottom wall 31 of thevessel 30 also provides means to re-suspend settled particles of solidswhenever the submerged gas evaporator is re-started after having beenshutdown for a period of time sufficient to allow suspended particles tosettle on or near the bottom wall 31.

As is known, submerged gas evaporation is a process that affectsevaporation by dispersing a gas within a liquid or liquid mixture, whichmay be a compound, a solution or slurry. Within a submerged gasevaporator heat and mass transfer operations occur simultaneously at theinterface formed by the dynamic boundaries of the discontinuous gas andcontinuous liquid phases. Thus, all submerged gas evaporators includesome method to disperse gas within a continuous liquid phase. The systemshown in FIG. 1 however integrates the functions of dispersing the gasinto the liquid phase, providing thorough agitation of the liquid phase,and mitigating entrainment of liquid droplets with the gas phase as thegas disengages from the liquid. Additionally, the turbulence and mixingthat occurs within the vessel 30 due to the flow pattern created bydispersion of gas into liquid within the confined volume 70 reduces theformation of large crystals of precipitates and/or large agglomerates ofsmaller particles within the vessel 30.

FIG. 2 illustrates a second embodiment of a submerged gas processor 110,which is very similar to the submerged gas evaporator 10 of FIG. 1 andin which elements shown in FIG. 2 are assigned reference numbers beingexactly 100 greater than the corresponding elements of FIG. 1. Unlikethe device of FIG. 1, the submerged gas processor 110 includes a baffleor a shield 138 disposed within the vessel 130 at a location slightlyabove or slightly below the fluid surface 180 and above the second end142 of the weir 140. The baffle or shield 138 may be shaped and sized toconform generally to the horizontal cross-sectional area of the confinedvolume 170. Additionally, if desired, the baffle 138 may be mounted toany of the gas inlet tube 122, the vessel 130 or the weir 140. Thebaffle 138 augments the force of gravity near the balance point bypresenting a physical barrier that abruptly and positively eliminatesthe vertical components of velocity and hence, momentum, of thegas/liquid mixture, thereby assisting the mixture to flow horizontallyoutward and over the weir 140 at the upper circulation gap 137.

As will be understood, the weirs 40 and 140 of FIGS. 1 and 2 may begenerally flat plates or may be curved plates that extend across theinterior of the vessel 30 between different, such as opposite, sides ofthe vessel 30. Basically, the weirs 40 and 140 create a wall within thevessel defining and separating the volumes 70 and 71 (and 170 and 171).While the weirs 40 and 140 are preferably solid in nature they may, insome cases, be perforated, for instance, with slots or holes to modifythe flow pattern within the vessel 10 or 110, or to attain a particulardesired mixing result within the volume 71 or 171 while still providinga substantial barrier between the volumes 70 and 71 or 170 and 171.Additionally, while the weirs 40 and 140 preferably extend across thevessels 30 and 130 between opposite walls of the vessels 30 and 130,they may be formed into any desired shape so long as a substantialvertical barrier is formed to isolate one volume 70 (or 170) closest tothe gas inlet tube 22 from the volume 71 (or 171) on the opposite sideof the weir 40, 140.

FIG. 3 illustrates a cross-sectional view of a further submerged gasprocessor 210 having a weir 240 that extends around a gas inlet tube222. The submerged gas processor 210, which may be a submerged gasevaporator, a submerged gas chemical reactor or a combination submergedgas evaporator/chemical reactor, generally speaking has evaporativecapacity equivalent to approximately 10,000 gallons per day on the basisof evaporating water from process liquid. A combustion device (not shownin FIG. 3) delivers approximately 2,200 standard cubic feet per minute(scfm) of combustion gas at 1,400° F. or approximately 11,058 actualcubic feet per minute (acfm) to the gas inlet tube 222. While thedimensions of the submerged gas processor 210 are exemplary only, theratios between these dimensions may serve as a guide for those skilledin the art to achieve a desirable balance between three desirableprocess results including: 1) preventing the formation of large crystalsof precipitates and/or agglomerates of solid particles while maintainingsolid particles as a homogeneous suspension within the process liquid bycontrolling the degree of overall mixing within vessel 230; 2) enhancingthe rates of heat and mass transfer and any desirable chemical reactionsby controlling the turbulence and hence interfacial surface area createdbetween the gas and liquid phases within confined volume 270; and 3)mitigating the potential of entraining liquid droplets in the gas as thegas stream disengages from the liquid phase at the liquid surface 280 bymaintaining a desirable and predominately horizontal velocity componentfor the gas/liquid mixture flowing outward over the second end 242 ofthe weir 240 and along the surface of the liquid 280 within vessel 230.As illustrated in FIG. 3, the submerged gas processor 210 includes avessel 230 with a dished bottom having an interior volume and a verticalgas inlet tube 222 at least partially disposed within the interiorvolume of the vessel 230. In this case, the gas inlet tube 222 has adiameter of approximately 20 inches and the overall diameter of thevessel 230 is approximately 120 inches, but these diameters may be moreor less based on the design capacity and desired process result asrelates to both gas and liquid flow rates and the type of combustiondevice (not shown in FIG. 3) supplying hot gas to the submerged gasprocessor. In this example the weir 240 has a diameter of approximately40 inches with vertical walls approximately 26 inches in length. Thus,the weir 240 forms an annular confined volume 270 within vessel 230between the inner wall of the weir 240 and the outer wall of the gasinlet tube 222 of approximately 6.54 cubic feet. In the embodiment ofFIG. 3, twelve sparge ports 224 are disposed near the bottom of the gasinlet tube 222. The sparge ports 224 are substantially rectangular inshape and are, in this example, each approximately 3 inches wide by 7¼inches high or approximately 0.151 ft² in area for a combined total areaof approximately 1.81 ft² for all twelve sparge ports 224. Thus, in thisexample the ratio of gas flow per unit sparge port area is approximately6100 acfm per ft² at the hot gas operating temperature within the gasinlet tube 222, in this case 1,400° F.

As will be understood, the combustion gas exits the gas inlet tube 222through the sparge ports 224 into a confined volume 270 formed betweenthe gas inlet tube 222 and a tubular shaped weir 240. In this case, theweir 240 has a circular cross-sectional shape and encircles the lowerend of the gas inlet tube 222. Additionally, the weir 240 is located atan elevation which creates a lower circulation gap 236 of approximately4 inches between a first end 241 of the weir 240 and a bottom dishedsurface 231 of the vessel 230. The second end 242 of the weir 240 islocated at an elevation below a normal or at rest operating level of theprocess fluid within the vessel 230. Further, a baffle or shield 238 isdisposed within the vessel 230 approximately 8 inches above the secondend 242 of the weir 240. The baffle 238 is circular in shape and extendsradially outwardly from the gas inlet tube 222. Additionally, the baffle238 is illustrated as having an outer diameter somewhat greater than theouter diameter of the weir 240 which, in this case, is approximately 46inches. However, the baffle 238 may have the same, a greater or smallerdiameter than the diameter of the weir 240 if desired. Several supportbrackets 233 are mounted to the bottom surface 231 of the vessel 230 andare attached to the weir 240 near the first end 241 of the weir 240.Additionally, a gas inlet tube stabilizer ring 235 is attached to thesupport brackets 233 and substantially surrounds the bottom end 226 ofthe gas inlet tube 222 to stabilize the gas inlet tube 222 duringoperation.

During operation of the submerged gas reactor 210, the combustion gasesare ejected through the sparge ports 224 into the confined volume 270between the outer wall of the gas inlet tube 222 and the inside wall ofthe weir 242 creating a mixture of gas and liquid within the confinedvolume 270 that is significantly reduced in bulk density compared to theaverage bulk density of the fluid located in the volume 290 outside ofthe wall of the weir 240. This reduction in bulk density of thegas/liquid mixture within confined volume 270 creates an imbalance inhead pressure at all elevations between the surface of the liquid 280within vessel 230 and the first end 241 of the weir 240 when comparingthe head pressure within the confined volume 270 and head pressurewithin the volume 290 outside of the wall of the weir 240 at equalelevations. The reduced head pressure within the confined volume 270induces a flow pattern of liquid from the higher head pressure regionsof volume 290 through the circulation gap 236 and into the confinedvolume 270. Once established, this induced flow pattern providesvigorous mixing action both within the confined volume 270 andthroughout the volume 290 as liquid from the surface 280 and alllocations within the volume 290 is drawn downward through thecirculation gap 236 and upward due to buoyancy through the confinedvolume 270 where the gas/liquid mixture flows outward over the secondend 242 of the weir 240 and over the surface of the liquid 280 confinedwithin the vessel 230.

Within confined volume 270, the induced flow pattern and resultantvigorous mixing action creates significant shearing forces that areprimarily based on the gross difference in specific gravity and hencemomentum vectors between the liquid and gas phases at all points on theinterfacial surface area of the liquid and gas phases. The shearingforces driven by the significant difference in specific gravity betweenthe liquid and gas phases, which is, generally speaking, of a magnitudeof 1000:1 liquid to gas, cause the interfacial surface area between thegas and liquid phases to increase significantly as the average volume ofeach discrete gas region within the mixture becomes smaller and smallerdue to the shearing force of the flowing liquid phase. Thus, as a resultof the induced flow pattern and the associated vigorous mixing withinthe confined area 270, the total interfacial surface area increases asthe gas/liquid mixture flows upward within confined volume 270. Thisincrease in interfacial surface area or total contact area between thegas and liquid phases favors increased rates of heat and mass transferand chemical reactions between constituents of the gas and liquid phasesas the gas/liquid mixture flows upward within confined volume 270 andoutward over the second end 242 of the weir 240.

At the point where gas/liquid mixture flowing upward within confinedvolume 270 reaches the elevation of the fluid surface 280 and havingpassed beyond the second edge 242 of the weir 240, the difference inhead pressure between the gas/liquid mixture within the confined volume270 and the liquid within volume 290 fluid is eliminated. Absent thedriving force of differential head pressure and the confining effect ofthe wall of the weir 240, gravity and the resultant buoyancy of the gasphase within the liquid phase become the primary outside forcesaffecting the continuing flow patterns of the gas/liquid mixture exitingthe confined space 270. The combination of the force of gravity and theimpenetrable barrier created by the baffle 238 in the vertical directioneliminates the vertical velocity and momentum components of the flowinggas/liquid mixture at or below the elevation of the bottom of the baffle238 and causes the velocity and momentum vectors of the flowinggas/liquid mixture to be directed outward through the gap 239 created bythe second end 242 of the weir 240 and the bottom surface of the baffle238 and downwards near the surface of the liquid 280 within the vessel230 causing the continuing flow pattern of the gas/liquid mixture toassume a predominantly horizontal direction. As the gas/liquid mixtureflows outwards in a predominantly horizontal direction, the horizontalvelocity component continually decreases causing a continual reductionin momentum and a reduction of the resultant shearing forces acting atthe interfacial area within the gas/liquid mixture. The reduction inmomentum and resultant shearing forces allows the force of buoyancy tobecome the primary driving force directing the movement of thediscontinuous gas regions within the gas/liquid mixture, which causesdiscrete and discontinuous regions of gas to coalesce and ascendvertically within the continuous liquid phase. As the ascending gasregions within the gas/liquid mixture reach the surface 280 of theliquid within the vessel 230, buoyancy causes the discontinuous gasphase to break through the liquid surface 280 and to coalesce into acontinuous gas phase that is directed upward within the confines of thevessel 230 and into the vapor exhaust duct 260 under the influence ofthe differential pressure created by the blower or blowers (not shown inFIG. 3) supplying combustion gas to the submerged gas processor 210.

FIG. 4 is a top plan view of the submerged gas reactor 210 of FIG. 3illustrating the tubular nature of the weir 240. Specifically, thegenerally circular gas inlet tube 222 is centrally located and issurrounded by the stabilizer ring 235. In this embodiment, thestabilizer ring 235 surrounds the gas inlet tube 222 and essentiallyrestricts any significant lateral movement of the gas inlet tube 222 dueto surging or vibration such as might occur upon startup of the system.While the stabilizer ring 235 of FIG. 4 is attached to the supportbrackets 233 at two locations, more or fewer support brackets 233 may beemployed without affecting the function of the submerged gas reactor210. The weir 240, which surrounds the gas inlet tube 222 and thestabilizer ring 235, and is disposed co-axially to the gas inlet tube222 and the stabilizer ring 235, is also attached to, and is supportedby the support brackets 233. In this embodiment, the confined volume 270is formed between the weir 240 and the gas inlet tube 222 while thesecond volume 290 is formed between the weir 240 and the side walls ofthe vessel 230. As will be understood, in this embodiment, theintroduction of the gas from the exit ports 224 of the gas inlet tube220 causes process fluid to flow in an essentially toroidal patternaround the weir 240.

Some design factors relating to the design of the submerged gasprocessor 210 illustrated in FIGS. 3 and 4 are summarized below and maybe useful in designing larger or smaller submerged gas processors, whichmay be used as evaporators or as chemical reaction devices or both. Theshape of the cross sectional area and length of the gas inlet tube isgenerally set by the allowable pressure drop, the configuration of theprocess vessel, and the costs of forming suitable material to match thedesired cross sectional area, and, importantly, if direct fired, thecharacteristics of the burner that is coupled to the submerged gasprocessor. However, it is desirable that the outer wall of the gas inlettube 222 provides adequate surface area for openings of the desiredshape and size of the sparge ports which in turn admit the gas to theconfined volume 290. For a typical submerged gas evaporator, submergedgas reactor or combination submerged gas evaporator/reactor, thevertical distance between the top edge 242 of the weir 240 and the topedge of the sparge ports should be not less than about 6 inches andpreferably is at least about 17 inches. Selecting the shape and, moreparticularly, the size of the sparge port 224 openings is a balancebetween allowable pressure drop and the initial amount of interfacialarea created at the point where the gas is dispersed into the flowingliquid phase within confined volume 290. The open area of the spargeports 224 is generally more important than the shape, which can be mostany configuration including, but not limited to, rectangular,trapezoidal, triangular, round, oval. In general, the open area of thesparge ports 224 should be such that the ratio of gas flow to totalcombined open area of all sparge ports should at least be in the rangeof 1,000 to 18,000 acfm per ft², preferably in the range of 2,000 to10,000 acfm/ft² and more preferably in the range of 4,000 to 8,000acfm/ft², where acfm is referenced to the operating temperature withinthe gas inlet tube. Likewise, the ratio of the gas flow to the crosssectional area of the confined volume 270 should be at least in therange of 200 to 10,000 scfm/ft², preferably in the range of 50 to 6,000scfm/ft² and more preferably in the range of 1,000 to 2,500 scfm/ft².Additionally, the ratio of the cross sectional area of the vessel 230 tothe cross sectional area of the confined volume 270 (CSA_(vessel)) ispreferably in the range from three to one (3.0:1) to twelve-hundred toone (1200:1), is more preferably in the range from five to one (5.0:1)to one-hundred to one (100:1) and is highly preferably in the range ofabout ten to one (10:1) to fourteen to one (14:1). These ratios aresummarized in the table below. Of course, in some circumstances, otherratios for these design criteria could be used as well or instead ofthose particularly described herein.

TABLE 1 Preferred Ratios Embodiment Acceptable Range Preferred Rangeacfm/Total 4,000-8,000  1,000-18,000  2,000-10,000 CSA_(sparge ports)acfm/ft² acfm/ft² acfm/ft² scfm/ 1,000-2,000   200-10,000   500-6,000CSA_(confined volume) scfm/ft² scfm/ft² scfm/ft² CSA_(confined volume)/10:1-14:1  3.0:1-1,200:1  5.0:1-100:1 CSA_(vessel)

Turning now to FIG. 5, a submerged gas processor in the form of asubmerged gas reactor 310 is shown which is similar to the submerged gasevaporator of FIG. 1, and in which like components are labeled withnumbers exactly 300 greater than the corresponding elements of FIG. 1.Unlike the device 10 of FIG. 1, the submerged gas reactor 310 of FIG. 5does not include a pressurized burner but, alternatively, receives hotgases directly from an external source, which may be for example, aflare stack, a reciprocating engine, a turbine, or other source of wasteheat. The hot gases supplied by the external source may include gaseshaving a wide range of temperature and/or specific components and thesehot gases may be selected by one skilled in the art to achieve anycombination of a rate and degree of chemical reaction between componentsin the gas and liquid, a specific rate of evaporation or to create aspecific concentration of the process fluid.

FIG. 6 illustrates a submerged gas processor 410 which is similar to thesubmerged gas processors of FIGS. 1, 2 and 5, in which like elements arelabeled with reference numbers exactly 400 greater than those of FIG. 1.However, the submerged gas reactor 410 includes a jacket 482 at leastpartially surrounding the vessel 430. The jacket 482 may be used toassist in heating the fluid within the vessel 430, or alternately incooling the process fluid within the vessel 430 as may be desirable toprovide for a better or more complete evaporation process, or to providefor better reactions, such as chemical reactions or precipitation ofcomponents from the process fluid. Thus, the jacket 482 may be a heatingor a cooling jacket. Alternatively or in addition, the process fluid maybe heated or cooled by other or additional elements before entering thevessel 430, by recirculation from and to vessel 430 through other oradditional elements external to or even internal to the vessel 430, orby withdrawal from vessel 430 through other or additional elementsexternal to tank 430. For heating purposes the jacket 482, other oradditional external elements may be supplied using steam or other heattransfer fluids, electric resistive heating elements, hot gases, or anyother manner of providing heat. For cooling purposes the jacket 482,other or additional external elements may be supplied with water orother cold fluids such as antifreeze solutions or gas. Thus, in oneexample, the jacket 482 may allow gases having a wide range oftemperatures to be introduced into and used within the vessel 430 topromote a particular chemical reaction or series of reactions within thevessel 430 between the gas and the process fluid or to promote a desiredamount of evaporation within the vessel 430. The gas can be a purereactant, a mixture of reactants, or a mixture of reactant gases anddiluent gas or gases. In addition, selected degree of evaporation may beemployed in combination with a chemical reaction or any combination ofchemical reactions. Of course, such heating or cooling jackets may beused in, for example, the embodiment of the submerged gas processor ofFIGS. 1-5 or any other embodiment.

It will be understood that, because the weir and gas dispersionconfigurations within submerged gas processors illustrated in theembodiments of FIGS. 1-6 provide for a high degree of mixing, inducedturbulent flow and the resultant intimate contact between liquid and gaswithin the confined volumes 70, 170, 270, etc., the submerged gasprocessors of FIGS. 1-6 create a large interfacial surface area for theinteraction of the process fluid and the gas provided via the gas inlettube, leading to very efficient heat and mass transfer between gas andliquid phases and/or high rates of chemical reactions between componentswithin these two phases. Furthermore, the use of the weir and, ifdesired, the baffle, to cause a predominantly horizontal flow pattern ofthe gas/liquid mixture at the surface of the fluid process mixturemitigates or eliminates the entrainment of droplets of process liquidwithin the exhaust gas. Still further, the high degree of turbulent flowwithin the vessel mitigates or reduces the formation of large crystalsor agglomerates and maintains the mixture of solids and liquids withinthe evaporator/reactor vessel in a homogeneous state to prevent orreduce settling of precipitated solids. This factor, in turn, reduces oreliminates the need to frequently clean the reactor vessel and, in thecase of evaporation processes, allows the process to proceed to a veryhigh state of concentration by maintaining precipitates in suspension.In the event that such solids do form, however, they may be removed viathe outlet port 32 (FIG. 1) using a conventional valve arrangement.

While a couple of different types submerged gas processors havingdifferent weir configurations are illustrated herein, it will beunderstood that the shapes and configurations of the components,including the weirs, baffles and gas entry ports, used in these devicescould be varied or altered as desired. Thus, for example, while the gasinlet tubes are illustrated as being circular in cross section, thesetubes could be of any desired cross sectional shape including, forexample, square, rectangular, oval, etc. Additionally, while the weirsillustrated herein have been shown as flat plates or as tubular membershaving a circular cross-sectional shape, weirs of other shapes orconfigurations could be used as well, including weirs having a square,rectangular, oval, or other cross sectional shape disposed around a fireor other gas inlet tube, weirs being curved, arcuate, or multi-facetedin shape or having one or more walls disposed partially around a fire orgas inlet tube, etc. Also, the gas entry ports shown as rectangular mayassume most any shape including trapezoidal, triangular, circular, oval,or triangular.

Still further, as will be understood, the terms submerged gas reactor,submerged gas evaporator and submerged gas processor have been usedherein to generally describe and to include both submerged gasevaporators and submerged gas chemical reactors as well as otherdevices. As a result, any of the submerged gas processors described orillustrated herein may be used as evaporators or as chemical reactiondevices or both. Likewise, the principles described herein may be usedon a submerged combustion gas evaporator or reaction device, e.g., onethat combusts fuel to create the gas, or on a non-combustion gasevaporator or reaction device, e.g., one that accepts gas from adifferent source. In the later case, the gas may be heated gas from anydesired source, such as an output of a reciprocating engine or aturbine, a process fueled by landfill gas, or any other source of heatedgas. Such a reciprocating engine or turbine may operate on landfill gasor on other types of fuel. Of course, generally speaking, the submergedgas processors described herein may be connected to any source of wasteheat and/or may be connected to or include a combustion device of anykind that, for example, combusts one or a combination of a biogas, asolid fuel (such as coal, wood, etc.), a liquid fuel (such as petroleum,gasoline, fuel oil, etc.) or a gaseous fuel. Alternatively, the gas usedin the submerged gas processor may be non-heated and may even be at thesame or a lower temperature than the liquid or process fuel within thevessel, and may be provided to induce a chemical or physical reaction ofsome sort such as the formation of a desirable precipitate.

Still further, as will be understood by persons skilled in the art, theimproved submerged gas processors described herein may be operated incontinuous, batch or combined continuous and batch modes. Thus, in oneinstance the submerged gas processor may be initially charged with acontrolled amount of liquid to be processed and operated in a batchmode. In the batch mode, liquid feed is continuously added to thesubmerged gas processor to maintain a constant predetermined levelwithin the process vessel by replacing any components of the processfluid that are evaporated and/or reacted as the process proceeds. Oncethe batch process has reached a predetermined degree of concentration,completeness of a chemical reaction, amount or form of precipitate, orany combination of these or other desirable attributes, the process maybe shutdown and the desirable product of the process may be withdrawnfrom the submerged gas processor for use, sale or disposal. Likewise,the submerged gas processor may be initially charged with a controlledamount of liquid to be processed and operated in a continuous mode. Inthe continuous mode, liquid feed would be continuously added to thesubmerged gas processor to maintain a constant predetermined levelwithin the process vessel by replacing any components of the processfluid that are evaporated and/or reacted as the process proceeds. Oncethe fluid undergoing processing has reached a predetermined degree ofconcentration, completeness of a chemical reaction, amount or form ofprecipitate, or any combination of these or other desirable attributes,withdrawal of process fluid at a controlled rate from the process vesselwould be initiated. The controlled withdrawal of process fluid would beset at an appropriate rate to maintain a desirable equilibrium betweenthe rate of feed of the liquid and the gas, the rate of evaporation ofcomponents from the process liquid, and the rate at which the desiredattribute or attributes of the processed fluid are attained. Thus, inthe continuous mode, the submerged gas processor may operate for anindeterminate length of time as long as there is process feed liquidavailable and the process system remains operational. The combinedcontinuous and batch mode refers to operation where, for instance, theamount of available feed liquid is in excess of that required for asingle batch operation, in which case the process may be operated forrelatively short periods in the continuous mode until the supply of feedliquid is exhausted.

While certain representative embodiments and details have been shown forpurposes of illustrating the invention, it will be apparent to thoseskilled in the art that various changes in the methods and apparatusdisclosed herein may be made without departing from the scope of theinvention, which is defined in the appended claims.

1. A submerged gas processor comprising: a vessel having an interioradapted to hold a liquid; a tube disposed within the vessel and adaptedto transport a gas into the interior of the vessel; a weir disposedwithin the vessel adjacent the tube in a manner that defines a confinedvolume between the tube and the weir; an exhaust stack adapted totransport exhaust gases from the interior of the vessel; and a liquidinlet adapted to supply a liquid to the interior of the vessel; whereinthe weir includes a first weir end and a second weir end and is disposedwithin the vessel to define a first circulation gap between the firstweir end and a first wall of the vessel and to define a secondcirculation gap between the second weir end and a second wall of thevessel which enables liquid within the vessel to flow through the firstand second circulation gaps when gas is introduced into the vessel fromthe tube.
 2. (canceled)
 3. The submerged gas processor of claim 1,further including a baffle disposed proximate the second circulation gapand generally perpendicular to the weir, wherein the distance betweenthe second weir end and the baffle is in the range of 1 to 20 inches. 4.(canceled)
 5. The submerged gas processor of claim 1, further includinga baffle disposed proximate the second circulation gap and generallyperpendicular to the weir, wherein the baffle is attached to an interiorwall of the vessel. 6-7. (canceled)
 8. The submerged gas processor ofclaim 1, wherein a plurality of gas exit slots is disposed in the tube,the gas exit slots being sized to produce a ratio of gas flow in actualcubic feet per minute (acfm) out of the tube to a cross sectional areaof the gas exit slots in the tube in the range of approximately 1,000acfm/ft² to approximately 18,000 acfm/ft² when the operating temperatureof the gas flowing out of the tube is approximately 1400 degrees F. 9.The submerged gas processor of claim 1, wherein a plurality of gas exitslots is disposed in the tube, the gas exit slots being sized to producea ratio of gas flow in actual cubic feet per minute (acfm) out of thetube to the cross sectional area of the gas exit slots in the tube inthe range of approximately 2,000 acfm/ft² to approximately 10,000acfm/ft² when the operating temperature of the gas flowing out of thetube is approximately 1400 degrees F.
 10. (canceled)
 11. (canceled) 12.The submerged gas processor of claim 1, wherein a plurality of gas exitslots is disposed in the tube, the gas exit slots being sized to producea ratio of gas flow in standard cubic feet per minute (scfm) out of thetube to a cross sectional area of the confined volume in the range ofapproximately 200 scfm/ft² to approximately 10,000 scfm/ft².
 13. Thesubmerged gas processor of claim 1, wherein a plurality of gas exitslots is disposed in the tube, the gas exit slots being sized to producea ratio of gas flow in scfm out of the tube to a cross sectional area ofthe confined volume in the range of approximately 500 scfm/ft² toapproximately 6,000 scfm/ft². 14-21. (canceled)
 22. The submerged gasprocessor of claim 1, wherein the weir comprises a generally flat platemember.
 23. The submerged gas processor of claim 22, wherein thegenerally flat plate member extends across the interior of the vesselbetween opposite sides of the vessel.
 24. (canceled)
 25. The submergedgas processor of claim 1, wherein the tube is connected to a source ofwaste heat.
 26. The submerged gas processor of claim 25, wherein thesource of the waste heat is one or a combination of a landfill gasprocessing device, a reciprocating internal combustion engine operatingon landfill gas and/or a turbine operating on landfill gas. 27-29.(canceled) 30-33. (canceled)
 34. The submerged gas processor of claim 1,further including a baffle disposed within the vessel at or above an atrest fluid level of the vessel.
 35. The submerged gas processor of claim1, further including a baffle disposed within the vessel above thesecond end of the weir. 36-42. (canceled)
 43. The submerged gasprocessor of claim 1, wherein the weir comprises a generally flat platemember.
 44. The submerged gas processor of claim 43, wherein thegenerally flat plate member extends across the interior of the vesselbetween opposite sides of the vessel.
 45. (canceled)
 46. The submergedgas processor of claim 1, wherein the tube is connected to a source ofwaste heat. 47-51. (canceled)
 52. The submerged gas processor of claim1, wherein the gas tube is connected to a combustion device and thecombustion device combusts biogas.
 53. A method of processing a fluid ina gas reaction device having a weir disposed within a vessel to definefirst and second volumes within the vessel and a gas delivery tubeextending into the vessel into the first volume, comprising: supplyingfluid to the vessel at a rate sufficient to maintain a fluid surfacelevel in the vessel near or above a first end of the weir; providing gasthrough the gas delivery tube to force the gas through an exit in thegas delivery tube to cause mixing of the gas and the fluid within thefirst volume by creating a circular flow of fluid from the first volumearound the first end of the weir into the second volume and from thesecond volume around a second end of the weir and into the first volume;removing exhaust gases through an exhaust stack in the vessel; andremoving fluid from the vessel via a fluid exit.
 54. The method of claim53, further including removing fluid with suspended solid particulatefrom the vessel. 55-72. (canceled)